Known in the art is the mass-manufacturing of hollow, prismatic, monolithic reinforced-concrete construction elements of rectangular section for building stackable dwellings, such that it is possible to construct buildings from factory-made elements.
“Monolithic construction element” is taken to mean an element that is homogeneous from the point of view of the material composing it. In this respect, it is possible to conceive of several degrees of monolithism, which will be greater the greater the homogeneity that is achieved in the element.
This monolithism will be associated with greater structural strength, for the greater the monolithism is the fewer joints the element will have and, in general, the fewer weak spots.
In its patent ES 2 285 877 the applicant, with experience in the specific sector of modular construction elements manufacturing, describes a method for manufacturing modular elements that uses four prefabricated reinforced-concrete panels that will make up the four walls, sides, bottom and top, these last also called “floor slab” and “ceiling slab” respectively, of the prefabricated element. More specifically, this patent claims a preferred embodiment in which the prefabricated modular elements are obtained by attaching the aforesaid four walls to two steel frames. Although it is not mentioned in the patent, the four panels are made using a method known in the sector, by formworking on horizontal tables, for which purpose a self-compacting concrete can be used. Concreting on horizontal tables is essential for obtaining the utmost homogeneity of the panel so obtained, since the cement does not have to travel great distances, and the method also avoids disintegration due to vertical drop. Self-compacting concrete is taken to mean a concrete with fluidity characteristics.
However, although in this technique described each panel is homogeneous and can have high strength, the product so obtained is not monolithic, since all the joints at the edges are made once the panels have already been made. Similarly, although stabilisation and union by means of said frames has given satisfactory results, it does involve joints made after the various panels have set, and is therefore not optimum from the standpoint of overall monolithism, since the rigidity of the whole is mainly concentrated in the frames.
Besides, there already exist methods that permit relatively monolithically manufactured elements to be obtained. The most common is casting or concreting in fixed formwork during the process, with the final prismatic shape of said element. The concreting will thus inevitably be implemented in the vertical plane for the walls of the formwork that are mounted vertically, and this will give rise to disintegration of the concrete owing to the considerable distance that it has to travel.
This last disadvantage is aggravated when the aim is to obtain reinforced elements with thin walls, as the passage section for the liquid concrete is reduced, and it also comes up against the reinforcing bars already arranged in the formwork, thereby making the formation of blowholes/honeycombing in the end product highly likely, in addition to a probable lack of homogeneity of the material making it up. And this disadvantage is obviously rendered more acute when the dimensions of the final product are increased.
Another disadvantage of fixed formwork is the difficulty, where setting permits, of withdrawing the moulds that compose the formwork, particularly the interior ones.
Another solution is to use a rotating formwork, which allows successive formworking in the horizontal plane of the various walls by rotating the drum that contains the formwork. However, although this solution does allow a high degree of monolithism to be achieved, it also presents the following disadvantages:                The device is complex, since it calls for a large structure capable of driving a large mass in rotation. This therefore constitutes a clear limitation as regards the maximum dimensions of the element obtained.        Only elements of a single dimension can be obtained, so the method is not very versatile from the point of view of the product, unless additional moulds or fillers are employed.        Although it does allow mass-manufacturing of elements, the total manufacturing time of an element is about four times as long as the minimum setting time needed for each of the four walls of the element.        It presents problems of stripping (removal of formwork) when the element needs ribs, a necessary condition for any stackable modular system due to issues of making it lighter. In this respect the utilisation of added moulds which are removed once the piece has been withdrawn from the drum has been proposed. But this solution involves an added cost in auxiliary elements, in processing time and problems of tolerances, since the introduction of further stages and auxiliary elements inevitably gives rise to positioning errors.        
Other related inventions are disclosed in WO 9513172 A1 relating to a “Method of Manufacturing precast concrete units”, U.S. Pat. No. 4,207,042 A relating to a “Casting and erecting machine” and SU 1717368 A1 relating to a “Plant for manufacturing monolith volumetric products.”
It should be noted that the control of tolerances and measurements in the manufacturing processes described is limited, since in all cases there are many moving parts and manufacturing stages. This clearly limits the maximum number of floors that a building made by stacking of applicable modular elements can have. It is thus not obvious in this sector of the art that a method could be made available that permits modular construction elements such as those described to be obtained, having a high degree of monolithism and that can be mass-manufactured within an optimum time and with strict control of tolerances.